A universal staff mount like this one was likely used to affix a plane table, transit, circumference, or other similar surveying device to a tripod stand.

This intricately designed brass instrument (height 6.5 in.) consists of a mounting plate and a staff socket connected by a universal ball joint. A worm screw rotates an internal gear, which in turn exerts pressure on a leather gasket, thus fixing the ball in place. Decorative set screws also fix the mount in position. This mount was likely used to affix a plane table, transit, circumferenter, or other similar surverying device to a tripod stand.

Here's what the artifact looks like when disassembled: